The role of cytokines in disease progression in heart failure

Recent studies have identified the importance of biologically active molecules such as neurohormones as mediators of disease progression in heart failure. More recently it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.

Effect of amrinone on murine viral myocarditis

Management of acute viral myocarditis is still controversial. Amrinone, a noncatecholamine nonglycoside bipyridine agent, produces sustained improvement of cardiac function and symptomatology in congestive heart failure (CHF). Amrinone demonstrates phosphodiesterase inhibitory activity that is relatively selective for the major phosphodiesterase isozyme in cardiac muscles, PDE III, which specifically hydrolyzes cyclic 3'5' adenosine monophosphate (cAMP). We investigated the effects of amrinone in an animal model of acute CHF related to myocarditis caused by the encephalomyocarditis virus (EMCV). Female C3H mice were inoculated intraperitoneally (i.p.) with 500 plaque-forming units of EMCV in 0.1 ml of saline. A total of 96 mice were randomly assigned to four groups. Each animal was administered 0.2 ml of phosphate-buffered saline (PBS) containing amrinone at a concentration of 1, 10, or 50 mg/kg, or PBS as an infected control, injected i.p. once daily for 21 days, starting on day 1 after viral inoculation. Each group contains 20 to 30 mice. Infected untreated mice survived at 80% (n = 16), however, only 13% (n = 16) of mice treated with amrinone (50 mg/kg) survived (p < 0.01). Downregulation of cardiac cAMP occurred 1 day after the viral infection. Although amrinone (10 and 50 mg/kg) treatment significantly (p < 0.05) increased the cardiac cAMP content and the dose of 10 mg/kg could potentially retard death from CHF due to viral myocarditis. The higher (50 mg/kg) doses of amrinone may produce unfavorable effects when used to treat mammals with viral myocarditis and CHF.

Basic mechanisms in heart failure: the cytokine hypothesis

Although the development and progression of heart failure have traditionally been viewed as hemodynamic disorders, there is now an increasing awareness that the syndrome of heart failure cannot be simply and/or precisely defined solely in hemodynamic terms. The inability of the so-called hemodynamic hypothesis to explain the progression of heart failure has given rise to the notion that heart failure may progress as a result of the overexpression of an ensemble of biologically active molecules referred to generically as neurohormones. More recently, it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.

Three-dimensional structure of the gustatory cell in the mouse fungiform taste buds: a computer-assisted reconstruction from serial ultrathin sections

Taste buds in fungiform papillae of the mouse were examined with transmission electron microscopy and computer-assisted, three-dimensional reconstruction from serial ultrathin sections. In accord with observation by Murray (1971), four distinct cell types, type I, II, III and basal cells, were identified. Of these, only the type III cell made synaptic contacts with nerve terminals and contained both small, clear vesicles and dense-cored granules. The former vesicles were synaptic-type and accumulated in the cytoplasm just below the synaptic in membrane thickenings. This finding clearly indicates a sensory function for the type III cell. One to three type III cells were identified within a taste bud. The type III cell had at most eight synapses with nerve terminals. One nerve fiber making two synapses with the type III cell was occasionally observed in its terminal region.

Fine structure of Merkel corpuscles in the lingual mucosa of Japanese quail, Coturnix coturnix japonica

By electron microscopy, these corpuscles were found exclusively in the connective tissue just beneath the dorsal epithelium near the lateral margin of the tongue. Each consisted of 4-8 Merkel cells and flattened nerve terminals arranged alternately. The Merkel cell was characterized by dense-cored granules, with a diameter ranging from 120 to 180 nm, throughout the cytoplasm. The functional significance of the avian Merkel cell, i.e. a mechanoreceptor cell or a trophic cell with the axon, still remains enigmatic, as is the case with Merkel cells of other vertebrates.

The occurrence and fine structure of Merkel cells in the lingual epithelium of the turtle, Clemmys japonica

Electron microscopic examination of the lingual mucosa of the turtle, Clemmys japonica, revealed the occurrence of Merkel cells that shared many morphological features with Merkel cells in other vertebrates. Merkel cells were located exclusively in the basal portion of the epithelium near the taste buds. We also found occasional Merkel cells devoid of nerve contact. Nerve terminals approaching these non-innervated Merkel cells were occasionally found in the connective tissue just beneath these cells.

Occurrence of melanosome-containing Merkel cells in mammalian oral mucosa

The occurrence and fine structure of Merkel cells with melanosomes in the labial epithelium of the dog and cat were studied by electron microscopy. These melanosomes were polarized in the Merkel cell cytoplasm opposite to the major aggregation of dense-cored granules and the closely abutting nerve terminal. None of melanosomes was found in the Golgi complex region where a few immature dense-cored granules were observed. This may suggest that the melanosomes are not produced in the Merkel cell, but are taken from the melanocytes like in keratinocytes. The possible phagocytotic ability of Merkel cells is discussed.

Fine structure of the Herbst corpuscles in the lingual mucosa of the finch, Lonchura striata

The ultrastructure of Herbst corpuscles in the lingual mucosa of the finch, Lonchura striata var. domestica, was examined by light and electron microscopy. Numerous Herbst corpuscles were found at the top of connective tissue papillae just beneath the dorsal epithelium. The Herbst corpuscle was composed of an outer capsule, inner core and central axon. The central axon was discoid in shape and immunoreactive for NSE-antiserum. The central axon was surrounded by compactly stacked layers of thin lamellae of lamellar cell processes. Since these lamellae did not completely encircle the axon as seen in cross sections, they displayed a symmetrical longitudinal cleft dividing the inner core into bilateral halves. Numerous axonal spines were seen to extend from the Y-axis of the axolemma into the cleft and occasionally into the cytoplasmic invagination of the lamellar cell body in the inner core. A number of clear and dense-cored vesicles were seen in the axoplasm near the base of axonal spines. Further, the omega-shaped coated invaginations were occasionally found on the axolemma near those places. These findings suggest that the area nearby the axonal spine in the central axon of the Herbst corpuscle is a site active both metabolically and functionally.

Factors to be considered in the evaluation of bioavailability and bioequivalence of topical formulations

In this paper, an attempt is made to find functional definitions of bioavailability and bioequivalence for topical products and to examine critical factors that influence topical bioavailability and bioequivalence. A physical model approach for quantifying the problem and increasing our understanding is presented here. The key assumptions are (1) that the target site is in the lower epidermis (basal layer) or in the dermis, and (2) that it is the thermodynamic activity (i.e., the free drug concentration, C*, of the active drug species) at the target site that is the true correlate of drug effectiveness. Studies initiated to implement the physical model approach involved first validating a 'three-tiered' model for finite dose drug uptake/transport in skin with experimentally determined input parameters (partition coefficient, K, and steady-state permeability coefficients, P, for the stratum corneum, viable epidermis, and dermis). Hydrocortisone was used as the model drug with hairless guinea pig skin as the model membrane. The physical model is used to show, via the C* concept, how formulation factors may influence bioavailability and bioequivalence. Finally, a method is presented for predicting the efficacy of topical formulations employing appropriate in vitro data and physical model calculations.